Booting from DVD drive or USB-Stick for installation, or support for booting over network (you need to setup PXE by yourself, look also at PXE boot installation) or an existing installation of openSUSE, more information at Installation without CD

The GRUB bootloader co-operates with other operating systems on the same machine. openSUSE can be installed on one free harddisk partition, while preserving existing installations on other partitions.